From a uk ex-instructor point of view knowing your going commercial
CRP-5 which is the commercial nav computer which is used in the exams. But you won't need it until you start the NAV phase of training.
Books: EBAY has most of them but see which ones your school uses both are as good as each other.
Clip Board initially you don't need one but as you go on for PPL a A5 one will do and some means of attaching it to your knee. Or you can purchase at great cost one from a pilot shop. A4 later for instrument flying .
chart wise they will sell them in the school hopefully unfolded. Then you instructor can show you how to fold it properly without fighting against the creases that the shop has put in it. Don't go near Jeps charts until after you have got your PPL. It will just confuse you.
Rule's pens and all the rest you can get from tescos as you need them.
And a watch any one will do that is clear digital or analogue as you prefer.
The log book is the biggest first thing you need to get quickly
Basically get one which says commercial and either JAR or EASA compliant. Don't get a FAA compliant one.